Daniel-Sebastian Dohle

Aortic remodelling in aortic dissection after frozen elephant trunk

OBJECTIVES Frozen elephant trunk (FET) can be used for continuous downstream aorta treatment in acute aortic dissection (AAD) and chronic aortic dissection (CAD). The study reports the changes in the lumen volumes along the downstream aorta towards remodelling. METHODS In 70 patients (22 CAD, 48 AAD), pre-, postoperative and at least the 1-year follow-up aortic imaging was available. Volume changes of aortic lumen (AL) and true lumen (TL) between examinations along the stent graft aortic segment (A), downstream to coeliac trunk (B) and distally to bifurcation (C) were used for quantification. TL increase >10% with stable AL or AL decrease >10% with stable TL were classified as positive, changes within a 10% threshold as stable, and all other changes as negative remodelling. RESULTS In AAD, positive or stable remodelling occurred in A (90%), B (65%), C (58%) within 1 year, thereafter in 26 patients (follow-up: 47 ± 21 months) in A (92%), B (65%), C (62%). Negative remodelling in ≥2 segments was found in 5/26 (19%) patients. In CAD, positive or stable remodelling occurred in A (100%), B (86%), C (77%) within 1 year, thereafter in 16 patients (follow-up: 46 ± 20 months) in A (75%), B (44%), C (38%). Negative remodelling in ≥2 segments was found in 7/16 (43%) patients, 5 underwent reintervention, and stabilized thereafter. CONCLUSIONS FET facilitates positive remodelling in AAD and CAD down to stent graft level. Distally, 20% AAD and 40% CAD patients remain at risk for secondary reintervention, and can be identified by negative remodelling in ≥2 segments in the follow-up examinations.

Six-year experience with a hybrid stent graft prosthesis for extensive thoracic aortic disease: an interim balance

OBJECTIVES To avoid a two-stage surgical approach for complex thoracic aortic disease with its additive mortality and morbidity, a hybrid stent graft prosthesis was introduced 6 years ago for simultaneous treatment of the ascending, arch and descending aortas, relying proximally on a surgical suture line with an integrated distal stent graft for downstream splinting. We report the mid-term single-centre experience. METHODS Between January 2005 and March 2011, 77 patients (mean age 59 years, male 75%) with acute (AAD, n = 39) or chronic aortic dissection (CAD, n = 23) DeBakey type I or an extensive thoracic aortic aneurysm (TAA, n = 15) underwent one-stage repair. Periodic follow-up studies (100%, mean 29 months) included repeat aortic computed tomography imaging. Major adverse events (MAEs) were defined as permanent stroke, spinal cord injury and dialysis. RESULTS In-hospital mortality was 10% (8 of 77). The incidence of MAE in AAD, CAD and TAA was 5, 13 and 20%, respectively. At the last follow-up, the complete thrombosis of the thoracic false lumen was 92% for AAD, 91% for CAD and the full exclusion of aneurysms 100% in TAA. Throughout the follow-up, freedom from aortic disease-related death was 93% and 5-year survival 79%. Freedom from distal reoperation was 94% in AAD, 95% in CAD and 100% in TAA and the incidence of distal stent graft extension 10% (8 of 77). CONCLUSIONS The durable hybrid one-stage repair of complex thoracic aortic disease is feasible with acceptable mortality. Distal reintervention is infrequent and associated with low risk; thus, the indication for the optimization of the peripheral flow using the endovascular aortic repair techniques is gradually widened.

Remote ischemic preconditioning: the surgeon's perspective.

Since cardiac surgery began, surgeons have aimed to find methods of minimizing myocardial injury resulting from ischemia and reperfusion. The concept of somehow conditioning the heart in order to attenuate ischemia and reperfusion-related injury has evolved in cardiovascular research over decades, from ischemic preconditioning and postconditioning to, more recently, remote ischemic preconditioning (and postconditioning). Although many strategies have proven to be beneficial in the experimental arena, a few have been successfully translated into clinical practice. Remote ischemic preconditioning, with the use of brief episodes of ischemia and reperfusion of vascular territories remote from the heart, has been shown convincingly to decrease myocardial injury. To date, the translation of this powerful innate mechanism of myocardial and/or multiorgan protection from the animal lab to the operating theatre, using transient occlusion of blood flow to the upper limb with a blood-pressure cuff before cardiac surgery, has shown promising results, with several proof-of-principle and first randomized controlled clinical trials reporting benefits for patients undergoing cardiac surgery. If the efficacy of remote ischemic preconditioning can be conclusively proven, the clinical applications in cardiac surgery could be almost infinite, providing multiorgan protection in various surgical scenarios.

Transient dilutional acidosis but no lactic acidosis upon cardiopulmonary bypass in patients undergoing coronary artery bypass grafting

Introduction Dilutional acidosis may result from the introduction of a large fluid volume into the patients’ systemic circulation, resulting in a considerable dilution of endogenous bicarbonate in the presence of a constant carbon dioxide partial pressure. Its significance or even existence, however, has been strongly questioned. Blood gas samples of patients operated on with standard cardiopulmonary bypass (CPB) were analyzed in order to provide further evidence for the existence of dilutional acidosis. Material and methods Between 07/2014 and 10/2014, a total of 25 consecutive patients scheduled for elective isolated coronary artery bypass grafting with CPB were enrolled in this prospective observational study. Blood gas samples taken regularly after CPB initiation were analyzed for dilutional effects and acid-base changes. Results After CPB initiation, hemoglobin concentration dropped from an average initial value of 12.8 g/dl to 8.8 g/dl. Before the beginning of CPB, the mean value of the patients’ pH and base excess (BE) value averaged 7.41 and 0.5 mEq/l, respectively. After the onset of CPB, pH and BE values significantly dropped to a mean value of 7.33 (p < 0.0001) and –3.3 mEq/l (p < 0.0001), respectively, within the first 20 min. In the following period during CPB they recovered to 7.38 and –0.5 mEq/l, respectively, on average. Patients did not show overt lactic acidosis. Conclusions The present data underline the general existence of dilutional acidosis, albeit very limited in its duration. In patients undergoing coronary artery bypass grafting it seems to be the only obvious disturbance in acid-base homeostasis during CPB.

Thoracic Endovascular Repair of Complicated Penetrating Aortic Ulcer: An 11-Year Single-Center Experience.

Purpose: To analyze an 11-year single-center experience of treating complicated penetrating aortic ulcer (PAU) using thoracic endovascular aortic repair (TEVAR). Methods: This study included 63 consecutive patients (mean age 69.1±11.5 years; 40 men) with complicated PAU (42 symptomatic, 22 with rupture) who underwent TEVAR between 2002 and 2013. The PAUs were located in the aortic arch (n=11), the descending thoracic aorta (n=43), and the thoracoabdominal aorta (n=9). Results: TEVAR was performed within 14 days of diagnosis in 33 (52.3%) cases (19 ruptures treated immediately); the other 30 (47.6%) patients had an average interval between diagnosis and intervention of 40±39 days. Technical success was 98.4% (62/63). One patient had a type I endoleak after stent-graft repair of a PAU in the aortic arch without great vessel transposition; another procedure was required for carotid-subclavian bypass and proximal stent-graft extension. No patient experienced spinal cord ischemia after TEVAR. Five (7.9%) patients died in-hospital; 3 had severe cardiac complications, 1 died from complications of aortic rupture, and the other succumbed to septic shock. Mean follow-up was 45.6±47.2 months, during which 12 (19.0%) patients needed a secondary intervention because of late endoleaks (n=4, 6.3%) or new complications due to disease progression. Multivariate analysis indicated that a PAU depth >15 mm was an independent predictor of mortality (hazard ratio 6.92, p=0.03). In the biomarker analysis, symptomatic patients had significantly higher D-dimer and troponin levels compared to asymptomatic patients [559.5±460.7 vs 283.2±85.2 µg/L (p=0.016) and 0.22±0.61 vs 0.02±0.03 ng/mL (p=0.04), respectively]. Conclusion: Patients with PAU suffer from underlying severe atherosclerotic disease and have a significant number of cardiovascular comorbidities that lead to relevant mortality and morbidity after TEVAR. As a PAU diameter >15 mm represented high risk for disease progression, these patients may be candidates for early intervention. D-dimer levels may help identify patients at risk and with progression of PAU.

Validation of intravascular ultrasound for measurement of aortic diameters: Comparison with multi-detector computed tomography

Abstract Introduction: Intravascular ultrasound (IVUS) provides real-time imaging of aortic pathology during aortic interventions. The objective of the present study was to validate IVUS measurements using computed tomography (CT) angiography in a sufficiently large cohort. Material and methods: From October 2010 to February 2014, 57 consecutive patients with acute aortic syndrome underwent both IVUS and spiral CT for a total of 509 comparable thoracic aorta segments. Minimum, maximum, and mean diameters were determined at each measurement point. Results: IVUS measurements of the thoracic aorta (aortic root, brachiocephalic trunk, left common carotid artery, left subclavian artery) ranged from 18–48.5 (mean 33.0) mm, versus 18–48.4 (mean 31.7) mm on CT, with a significant mean difference of 5.1% (p < 0.05). The correlation between methods was generally good, but IVUS tended toward larger diameters than CT in the aortic arch, especially the left subclavian artery. In 78% of measurement sites, total mean diameters were larger on IVUS measurements of the thoracic aorta than on CT measurements. Conclusion: IVUS is a reliable tool for measuring aortic diameter, especially in the descending part of the aorta. However, its pitfalls must be considered to prevent choosing an incorrectly sized stent graft in the acute setting of thoracic endovascular aortic repair.

Heart-Type Fatty Acid Binding Protein and Ischemia-Modified Albumin for Detection of Myocardial Infarction After Coronary Artery Bypass Graft Surgery

BACKGROUND Heart-type fatty acid binding protein (hFABP) and ischemia-modified albumin (IMA) have been put forward as novel biomarkers to detect myocardial injury shortly after onset of ischemia. We compared hFABP and IMA with cardiac troponin I (cTnI) for speed and reliability in the diagnosis of perioperative myocardial infarction (PMI) after coronary artery bypass graft surgery (CABG). METHODS In all, 210 consecutive patients undergoing isolated CABG with cardiopulmonary bypass were enrolled in a prospective study. Blood samples were taken perioperatively and throughout the first 72 hours after surgery; clinical data and events were recorded. In cohort A, serum concentrations of hFABP and cTnI were measured using a combined quantitative bedside assay. In cohort B, IMA and cTnI serum concentrations were measured using an albumin cobalt binding test. Perioperative myocardial infarction was defined using a cTnI cutoff of greater than 10.5 ng/mL occurring within 24 hours of CABG or new electrocardiographic changes. RESULTS In cohort A, 14 patients were identified with PMI (group 1), whereas 94 had no PMI and served as controls (group 2). Both hFABP and cTnI were increased in group 1 as compared with group 2 (p < 0.001). Although cTnI did not differ before 12 hours, hFABP diverged much earlier, at 1 hour postoperatively (p < 0.001). An hFABP concentration of 20 μg/mL at 1 hour detected PMI with an area under the curve of 77.1%. In cohort B, 18 patients were identified with PMI (group 3), and 84 patients served as controls (group 4). No difference in cTnI values could be observed between the groups until 12 hours postoperatively. Ischemia-modified albumin failed to differentiate at any postoperative time point; the low discriminative power of IMA was confirmed with an area under the curve of 53.3% at 1 hour, 48.5% at 6 hours, and 39.3% at 12 hours postoperatively. CONCLUSIONS Heart-type fatty acid binding protein is a sensitive and rapid biomarker that detected PMI reliably at 1 hour after CABG, much earlier than cTnI. The diagnostic value of IMA for detection of PMI appears to be very limited in this setting.

Impact of Acute Intestinal Ischemia and Reperfusion Injury on Hemodynamics and Remote Organs in a Rat Model

Background Acute mesenteric ischemia following cardiovascular surgery is a rare but fatal complication. We established a new rat model for hemodynamic monitoring during mesenteric ischemia/reperfusion (I/R) and evaluated the impact of mesenteric I/R on hemodynamics and remote organ injury. Methods Mesenteric I/R was induced in male Wistar rats by superior mesenteric artery occlusion for 90 minutes, followed by 120 minutes of reperfusion. Before I/R, ventilation and hemodynamic monitoring including mean arterial blood pressure (MAP) and cardiac output (CO) were established. During reperfusion Geloplasma (I/R + Geloplasma, N = 6) and Ringers solution (I/R + Ringer, N = 6) were titrated according to CO and compared with I/R without volume resuscitation (I/R only, N = 6) and a sham group (sham, N = 6). Blood samples were regularly taken for serum marker measurements. After reperfusion organs were harvested for histology studies. Results After acute mesenteric I/R, MAP and CO decreased (p < 0.01) while systemic and pulmonary vascular resistance increased (p < 0.01) continuously in the I/R group. Volume substitution according to CO initially stabilized hemodynamic parameters, but CO declined independently in the late stage. Compared with the I/R + Ringer group, the I/R + Geloplasma group required less volume for resuscitation (p < 0.01), experienced less metabolic acidosis. I/R groups had more organ injuries, more neutrophils sequestration, and higher creatine phosphokinase‐MB levels than sham group. Conclusion A new model for CO monitoring after mesenteric I/R injury demonstrated severe hypovolemic shock during reperfusion followed by remote myocardial and lung injury. Far less colloid volume is needed for hemodynamic stabilization after I/R compared with crystalloid volume.

The impact of entries and exits on false lumen thrombosis and aortic remodelling

OBJECTIVES In DeBakey Type I acute aortic dissection, the frozen elephant trunk technique is used for the combined treatment of both the proximal and distal thoracic aorta. Anatomical characteristics of the distal aorta and their impact on false lumen (FL) thrombosis and aortic remodelling were analysed in this study. METHODS Sufficient pre‐, postoperative, and at least one 1‐year follow‐up computed tomography data sets were available for 63 of 94 patients treated with the frozen elephant trunk for Type I acute aortic dissection between March 2005 and March 2015. Aortic remodelling and FL thrombosis quotients were calculated volumetrically at the stent graft level (A), from A to the coeliac trunk (B) and from B to the bifurcation (C) and were correlated with the number and size of entry tears and aortic branches arising from the FL (exits) in each segment. RESULTS Positive or stable remodelling was found in Segments A (94%), B (64%) and C (54%), and the FL thrombosis quotient was 98% in A, 68% in B and 39% in C within the first year. FL thrombosis correlated negatively with the total size of the entry (P<0.001) and the number of exits (P<0.001) and positively with the number of true‐lumen branches (P<0.001). The exit number was a risk factor for FL patency and a predictor of negative remodelling. CONCLUSIONS Using frozen elephant trunk technique to treat Type I acute aortic dissection facilitates positive or stable remodelling in nearly all patients at the stent graft level and distally in two‐thirds of the patients. FL thrombosis and aortic remodelling are negatively influenced by the number of exits. New endovascular concepts aiming at reducing the number of exits may prevent negative remodelling.

Postoperative Compensatory Ammonium Excretion Subsequent to Systemic Acidosis in Cardiac Patients

Background Postoperative acid-base imbalances, usually acidosis, frequently occur after cardiac surgery. In most cases, the human body, not suffering from any severe preexisting illnesses regarding lung, liver, and kidney, is capable of transient compensation and final correction. The aim of this study was to correlate the appearance of postoperatively occurring acidosis with renal ammonium excretion. Materials and Methods Between 07/2014 and 10/2014, a total of 25 consecutive patients scheduled for elective isolated coronary artery bypass grafting with cardiopulmonary bypass were enrolled in this prospective observational study. During the operative procedure and the first two postoperative days, blood gas analyses were carried out and urine samples collected. Urine samples were analyzed for the absolute amount of ammonium. Results Of all patients, thirteen patients developed acidosis as an initial disturbance in the postoperative period: five of respiratory and eight of metabolic origin. Four patients with respiratory acidosis but none of those with metabolic acidosis subsequently developed a base excess > +2 mEq/L. Conclusion Ammonium excretion correlated with the increase in base excess. The acidosis origin seems to have a large influence on renal compensation in terms of ammonium excretion and the possibility of an overcorrection.